1,721,010 research outputs found
( 1 S, R s )-6,7- Dimetho xy-N-methyl-1-(p-tolylsulfinylmethyl)- l-trifluoromethyl-l,2,3,4- tetrahydroisoquinoline
No full textThe title compound, C21H24F3NO3S, is an intermediate
in the synthesis of enantiomerically pure alkaloids; the
molecular structure has been determined to establish its
stereochemistry. The molecular conformation is largely
determined by intramolecular interactions, while the packing in the crystal does not show any unusual
feature
Secondary Mould Metabolites: Part 47. Isolation and Structure Elucidation of Clavilactones A-C, New Metabolites from the Fungus Clitocybe Clavipes
No full textEnergy calculations for isotactic polypropylene: A contribution to clarify the beta crystalline structure
No full textAn analysis of the crystal structure of the β polymorph of isotactic polypropylene (β-iPP) is carried out with the methods of molecular mechanics, taking into account simultaneously intra- and intermolecular interactions. Results indicate that efficient crystal packing may be achieved in a number of different, nearly isoenergetic arrangements, most of them showing the features of frustration. This fact may well be due to the low density of β-iPP as compared to its other crystalline polymorphs. The most stable β-iPP structure is found in space group P31. Up−down disordering modes, found also in α- and γ-iPP, have marginally higher energy and give rise to P3121 symmetry, without superposition of methyl groups belonging to anticlined chains. This structure, involving random up−down disordering, is thus proposed as the best average structure for individual β-iPP domains. Mechanisms for twinning among different domains are also investigated in order to explain the observed hexagonal symmetry of electron diffraction patterns
Palladium(II) and platinum(II) η3-methylallyl trichlorotin complexes. Part 3. Crystal structure analysis of [Pt(η3-C4H7)(cod)] 2[Pt(η3-C4H7)(SnCl 3)3] (cod = cyclo-octa-1,5-diene)
No full textThe dimer [Pt(η3-C4H7)Cl2] reacts with cyclo-octa-1,5-diene (cod) and SnCl2 to give [Pt(η3-C4H7) (cod)]2 [Pt(η3-C4H7) (SnCl3)3] (1). The compound crystallizes as discrete anionic and cationic platinum(II) complexes in space group P1 with a = 13.256(4), b = 19.960(4), c = 8.615(3) Å, α = 101.75(2), β = 104.69(2), and γ = 86.62(2)°. The anionic complex displays a distorted square-pyramidal co-ordination while the two isostructural cations have irregular square-planar co-ordination. Analysis of bond distances using SnCl3 as a probe suggests that the trans influence of the methylallyl ligand is comparable to that of olefin ligands. While no n.m.r. data are available for (1) due to its very poor solubility, n.m.r. results for the palladium(II) analogue (2) obtained by the same synthetic route are compatible with the structure determined for (1)
Crystallographic and nuclear magnetic resonance studies of carbonyl(η3-methylallyl)(trichlorostannyl) complexes of platinum(II) and palladium(II)
No full textThe complexes [M(η3-C4H7)(SnCl3)(CO)] [C4H7 = 2-methylallyl, M = Pt(1) or Pd(2)] have been prepared and characterized. Their solution behaviour has been studied by n.m.r. spectroscopy, the compounds being dynamic through dissociation of the CO ligand. The X-ray structures of (1) and (2) are reported. Complex (2) is the first mononuclear palladium carbonyl to be characterized by X-ray diffraction. The different stabilities of the two isostructural complexes are correlated with the subtle differences in bonding observed in the crystal structures
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